The eurozone will have to erect a larger financial firewall to combat the region's sovereign debt crisis before other countries pour more cash into the International Monetary Fund.

The calls on the eurozone to boost its war chest dominated the summit of Group of 20 Finance Ministers and Central Bank Governors (G20) in Mexico City on the weekend, with top officials including United States treasury secretary Timothy Geithner saying it was essential to prevent more fallout worldwide.

In a statement released after the summit, the G20 said: "Euro area countries will reassess the strength of their support facilities in March.

"This will provide an essential input in our ongoing consideration to mobilise resources to the IMF."

IMF managing director Christine Lagarde said she was encouraged by the meeting's outcome.

"There was progress at the technical level, especially a broad agreement that an increase in IMF resources could be done through bilateral borrowing and note purchase agreements," Ms Lagarde said.

"We have used this model before, and we know it can work quickly."

But Ms Lagarde warned that the world economy was still not out of the "danger zone".

"The G20 countries must now strengthen resilience to further shocks that could result from still fragile financial systems, high public and private debt and higher world oil prices," Ms Lagarde said.

"Of equal concern is unemployment, which is still too high in many countries."

At a crunch two-day summit in Brussels starting on Thursday night (AEDT), European Union leaders will debate whether to combine their current firewall, the European Financial Stability Facility (EFSF), with a permanent pot due to come into effect in July.

This would give the debt-wracked 17-nation eurozone a total fund of some 750 billion euros ($944.8 trillion).

To add even more firepower, the eurozone has called on countries outside the bloc to bolster IMF resources.

The IMF has said the fund needs an additional $466 billion.

"Progress on this strategy will be reviewed at the next minister meeting in April," the G20 statement said.

German roadblock

Eurozone countries already have committed 150 billion euros ($188.1 billion) to the IMF to reassure markets they have the resources to tackle a re-emergence of the crisis.

But countries outside the zone, including the US, Britain, Japan and China, insisted at the G20 meeting that the eurozone first put its hand in its pocket.

Britain's Finance Minister George Osborne said a trade-off had to be made.

The major obstacle to an increase in the eurozone firewall remained Germany, the bloc's top economy and political powerhouse.

Finance minister Wolfgang Schaeuble made no bones of Berlin's opposition to pouring in more cash to the pot, saying it "didn't make any economic sense".

Mr Schaeuble also played down the chances of success at the summit on March 1-2, saying that a decision on a strengthened firewall would be taken "in the course of March", recalling that "March runs from 1 to 31"

Although it pressured Europe to sort out its problems, the G20 statement also praised policymakers for measures already carried out, notably securing a second bailout package for Greece.

The statement also said the top economies were "alert to the risks of higher oil prices and welcome the commitment by producing countries to continue to ensure adequate supply".

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